Saw-tooth oscillation generator



Oct- 24, 19'50; ;A.M. sPooNr-:R

" smv-Toom oscILLA'rIoN GENERATOR nedzoct. 19, 194s ARCHER MICHAEL SPOONER RNVENTOR Fried@ ATTORNEY A Patented Oct. 24, 1950 UNITED STATES PATENT OFFICE SAW-TOOTH OSCILLATIQN' GENERATOR Archer Michael Spooner, London, England, as-

signor to The Hartford National Bank & Trust Company, Hartford, Conn., as trustee Application October 19, 1945,V Serial No. 623,245 In Great Britain September 5, 1944 Section 1, Public Law 690, August 8, 194.6

Patentexpires September 5, 1964 three grids in which the first grid4 adjacent the cathode is adapted to function as a control electrode, the second grid as a screen or accelerating electrode and a third grid which will be referred to as an additional control electrode.

The present invention is concerned only with said-multi-electrode valves of a Ytype possessing the characteristic that when suitable operatingl accelerating electrodes, While the first and third.

grids act as before as control electrode andl additional control electrode respectively. A substantially resistiveload joined in thev circuitrof the second grid and any grids Whichmay be associated with it,.results in the said' current change producing a'voltage change across the said resistive.I loadfin thesame Y sense as the voltage change at the Vadditional control grid.

According to the invention a sawtooth oscilla.-V

tion generatorof the blocking oscillatortyperin cluding'a valve having at least control` gridland. anodeis combined witha synchronising-imp-ulse amplieror buffer stage incorporatingy a multielectrode Valve of the type specifiedA above inwhich in'V the said multielectrode valve, the-control-grid isf 5 Claims. (Cl. 25W-36,)

adaptedto; receive synchronisation impulsestheV l anode is connected through a resistance or ldirectly to a positive potentialv source, the'second gridfand, any vassociated grids being connected by'wayof aY substantially resistive impedance to apositive potential source -while the` additionalccontrol selec trode is coupled tothe control gridcof thesfirstsecond andassociated grids are coupled by Way ofa small condenser to the control grid of the first-mentioned valve.

A modification of the present invention consists in the control grid ofthe synchronising impulsev amplifier or buffer valve beingadapted by means of a negative bias to suppress the electron emission fromth'e *cathode of the said valve except when a synchronising impulse isreceived f The invention is particularly applicable to thermionic valves in which two electrode systems l Valve is joined internally to the control grid of the triode-section.

The linvention will now be described with reference to the accompanying drawing. AIn the figure a triode-hexode I is-shown, the third grid2 of the hexode section being internally connected to theV control grid S'of the triode section. The triode section is arranged in a blocking oscillator circuit, the usual over-coupled transformer being denoted by 5, while 5 and -'I represent respectively the customary resistance and condenser in the grid circuit ofthe triode section. If the anode 4 ofthe triode section is joinedl by way of theY trans'- former windingshown, to a suitable positive potential source e; g. byV shortv circuiting resistance 8*' the circuitoperates-With short bursts 0f radio oscillations cease whenv condenser I is charged to*` a certain value land recommence when this condenser has discharged by wayj of resistance G. The said short bursts of oscillation result incorresponding short-:pulses ofcurrent in theY anode circ-uit andby; connectingiresistance Band condenser 9 as shownasawtooth voltage is produced across the plates of condenser 9. t

In order that synchronising impulses may be applied tothe sawtooth oscillator the hexode section ofthetriode heXode I has its control (first) grid'l adapted to receive the said impulses byvv way ofY coupling condenser II and resistance I2. rlhe anode kvI3 of the hexode section is connected byway of aresistance Itto a suitable positive sourceof potential.. The second and fourth grids I5 I6 are joined. and connected by Way of re-` sstance II to a positive potential source, while grids I5, I6 are also joined by a small condenser I8 to the grid 3 of the triode section. The hexode section thereby behaves as a buffer stage with regard to synchronising impulses and if correctly set up amplification of these impulses may be obtained, which are then applied by way of condenser I8 to the blocking oscillator to enable synchronisation of the latter to be obtained in the known manner.

In addition to acting as a buffer stage with regard to synchronizing impulses the hexode seotion also takes part in the generation oi sawtooth oscillations by the triode section. The operation can be explained as follows: the impulse Voltage normally occurring at the control grid 3 of the triode section during the short bursts of radiofrequency oscillation referred to above which occur during the return stroke or yback of the sawtooth wave form, is transferred to third grid 2 by virtue of the direct connection between grids 2 and 3 and generates a voltage impulse in the same sense on the second and fourth grids I5, I6 of the hexode section. This voltage impulse at the second and fourth grids is transferred by the coupling condenser I8 back to grid 3 and results in an intensification of the voltage impulse at that grid, and therefore a corresponding increase in the anode current of the triode section. The time duration of the return stroke of the sawtooth oscillation is accordingly reduced, since the said anode current is obtained mainly from the charge on condenser 9, which is thereby discharged at an increased rate. This eifect is the main advantage of the present invention since the time of the return stroke or iiyback of the sawtooth wave form, which depends on the time taken to discharge condenser 9, is thereby reduced.

Currents owing in the hexode section may inuence the curvature of the long stroke of the sawtooth wave form produced by the blocking oscillator in which case a suitable negative bias may be applied to the control grid of the hexode in known manner whereby electronic emission from the cathode of the hexode section is substantially suppressed during the said long stroke, but is allowed when synchronising impulses of suicient amplitude are received.

Typical Values of the components of the circuit shown in the drawing for the generation of a 50 cycles/sec. time base voltage for television use, are as follows:

with an operating voltage of 250 v. as the high tension and -16 v. applied between the lower end of I 2 and earth. The transformer 5 may consist of two coils of litz wire, closely coupled and having a dust iron core through the coils.

If a pentode valve is employed in place of the hexode valve as described above, the circult arrangement diifers only in that the screen grid between the additional control electrode and the Condenser Resistance Resistance Resistance Condenser anode is omitted. In general this resultant modification will prove beneficial to the operation of the circuit.

I claim:

1. An oscillation generator comprising a blocking oscillator including a rst discharge tube system having at least control grid and anode electrodes, and a synchronizing impulse ampliiier for said oscillator, said amplifier including a second discharge tube system having at least control grid, accelerating grid, additional control grid and anode electrodes, the operating characteristic of said second tube system being such that with suitable operating potentials applied to said electrodes a change in potential at said control grid results in a current change in the same sense at said accelerating grid and a change in potential at said additional control grid results in a current change in the opposite sense at said accelerating grid, means to connect a positive potential t0 the anode of said second tube system, a load impedance, means to connect a positive potential through said impedance to the accelerating grid of said second tube system, a capacitor coupling the accelerating grid of said second tube system to the control grid of said first tube system, means connecting the additional control grid of said second tube system to the control grid of said first tube system, and means for applying synchronizing impulses to the control grid of said second tube system.

2. An oscillation generator comprising a blocking oscillator including a rst discharge tube system having at least control grid and anode electrodes, and a synchronizing impulse amplier for said oscillator, said amplifier including a second discharge tube system having in succession control grid, accelerating grid, additional control grid and anode electrodes, the operating characteristic of said second tube system being such that with suitable operating potentials applied to said electrodes a change in potential at said control grid results in a current change in the same sense at said accelerating grid and a change in potential at said additional control grid results in a current change in the opposite sense at said accelerating grid, means to connect a positive potential to the anode of said second tube system, a load impedance, means to connect a positive potential through said impedance to the accelerating grid of said second tube system, a capacitor coupling the accelerating grid of said second tube system to the control grid of said first tube system, means connecting the additional control grid of said second tube system to the control grid of said first tube system, and means for applying synchronizing impulses to the control grid of said second tube system.

3. An oscillation generator comprising a blocking oscillator including a first discharge tube system having at least control grid and anode electrodes, and a synchronizing impulse amplifier for said oscillator, said amplifier including a second discharge tube system having in successive arrangement a cathode, first, second, third and fourth grids and an anode, said rst grid acting as a control electrode, said second and fourth grids being connected together and acting as an accelerating electrode and said third grid acting as an additional control electrode, the operating characteristic of said second tube system being such that with suitable potentials applied to said electrodes a change in potential at said additional control electrode results in a current change in the opposite sense at said acceleratinggelectrode,

means to connect a positive potential to the anode of said second tube system, a load impedance, means to connect a positive potential through said impedance to the accelerating electrode of said second tube system, a capacitor coupling the accelerating electrode of said second tube system to the contro-l grid of said irst tube system, means connecting the additional control electrode of said second tube system to the control grid of said rst tube system, and means for applying synchronizing impulses tothe control grid of said second tube system.

4. An oscillation generator comprising a blocking oscillator including a first discharge tube system having at least control grid and anode electrodes, and a synchronizing impulse amplier for said oscillator, said amplifier including a second discharge tube system having in successive arrangement a cathode, rst, second, third and fourth grids and an anode, said rst grid acting as a control electrode, said second and fourth grids being connected together and acting as an accelerating electrode and said third grid acting as an additional control electrode, the operating characteristic of said second tube system being such that with suitable potentials applied tosaid electrodes a change in potential at said additional control electrode results in a current change in the opposite sense at said accelerating electrode,

means to connect a positive potential to the anode I of said second tube system, a load impedance, means to connect a positive potential through said impedance to the accelerating electrode of said second tube system, a capacitor coupling the accelerating electrode of said second tube system to the control grid of said rst tube system, means connecting the additional control electrode of said second tube system to the control grid of said first tube system, means to apply a negative cutoff bias to the control electrode of said second tube system, and means to apply synchronizing impulses to the control grid of said second tube system to overcome said cut-olf bias and render said second tube system conductive for the duration of the impulse.

5. An oscillation generator comprising a blocking oscillator including a rst discharge tube system having cathode, grid and anode electrodes, an over-coupled transformer having primary and secondary windings, one end of said primary being connected to grid of said rst tube system, one end of said secondary being connected to anode of said first tube system, a resistance-capacitance parallel network connected between the other end of said primary and cathode of said rst tube system, a charging condenser connected between the other end of said secondary and cathode of said rst tube system, a resistor, and

means to connect a positive potential to said otherend of said secondary through said resistor, and a synchronizing impulse amplifier for said oscillator, said amplifier including a second discharge tube system having in successive arrangement a cathode, rst, second, third and fourth grids and an anode, said first grid acting as a controll electrode, said second and fourth grids being connected together and acting as an accelerating electrode and said third grid acting as an additional control electrode, the operating characteristic of said second tube system being such that with suitable potentials applied to said electrodes a change in potential at said additional control electrode results in a current change in the opposite sense at said accelerating electrode, means to connect a positive potential to the anode of said second tube system, a load impedance, means to connect a positive potential through said impedance to the accelerating electrode of said second tube system, a capacitor coupling the accelerating electrode of said second tube system to the control grid of said rst tube system, means connecting the additional control electrode of said second tube system to the control grid of said rst tube system, means to apply a negative cut-oir bias to the control electrode of said second tube system, and means to apply synchronizing impulses to the control grid of said second tube system to overcome said cut-off bias and render said second tube system conductive for the duration of the impulse.

ARCHER MICHAEL SPOONER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,193,850 Andrieu et al. Mar. 19, 1940 2,297,742 Campbell Oct. 6, 1942 2,310,888 Bahring et al Feb. 9, 1943 2,363,822 Wendt Nov. 28, 1944 FOREIGN PATENTS Number Country Date 105,174 Australia Sept. 29, 1938 510,531 Great Britain Aug. 2, 1939 

